Electrically-wound clock



p l 1931- v c. HALL 1,800,016

ELECTRI CALLY WOUND CLOCK Filed April 12, 1928 Inventor":

ChesterLHaH ym w His Attorney.

Patented Apr. 7, 1931 3 u mmm PATENT OFFICE.

enema I. HALL, or roar wnm, INDIANA, ns sm'non T GENERAL ELECTRIC COI- PANY, A CORPORATION OF NEW YORK,

ELECTRICALLY-WOUND CLOCK Application filed April 12,

My invention relates to a constant torque motive mechanism which is suitable for general application but which is particularly adapted for use in spring driven clock movements where a small electric motor is employed for winding the spring.

7 The time keeping qualities of the ordinary han'd' wound spring driven clock movement is impaired by reason of the fact that the clock escapement is required to regulate the plications and cost. I

tions above mentioned it has been proposed through which the speed between wide limits pf the mainspring tension. In the eight day clock for example, when the spring is full wound, the escapement mechanism is su jected to considerably more tension than exists when the sprin is nearly unwound. As a result the beat o the escapement tends to vary somewhat with the tension of the main spring. I This vary-.

ing condition may be compensated for to some extent but at the expense of added com- To avoid the condi I provide means responsive tothe countertorque of the main spring for controlling the winding torque transmitted thereto from the winding motor. In the preferred form of my invention a worm gear is provided between the winding motor and the spring counter-torque is transmitted. The motor is of the conventional induction, disc, alternating current type, but

- has its stator element pivotally mounted. .An

adjustable helical spring serves to normally hold the stator in the maximum torque operating position. When the counter-torque 'of the main spring reaches a predetermined value, however, the torque required to rotate the disc armature is such as to overcome the force of the helical spring and the state! 1928. semi 110.26%),514.

shifts into a reduced torque position. The disc then stops or keeps moving justrenough to maintain the tension on the main spring substantially constan The features of my invention, which are considered novel and patentable, out in the appended claims. itself, however, will best be understood by reference to the following specification when considered in connection with the accomare pointed panying drawing in which Fig. 1 is an expanded perspective view of the invention ap lied to aclock.

ig. 2 is an enlarged view of the rewinding motor, illustrating the pivotally mounted stator.-

Fig. 3 is a detail view illustrating the normal operating position of the field poles and in dotted lines, the possible position when the counter-torque of the spring has reached a redetermined value.

eferring to Fig. 1, 10 indicates the main its spring of a clock mechanism havin outer end attached to a gear 11 and: driving the'minute hand 12 by means of pinion 13 and shaft 14. The hour hand 12' is driven through a set of back gears lfi. A standard spring esca'peme'nt 16 regulates the move-, ment of shaft 14 through pinion l7 and gear 18. The inner end of spring 10 is attached to shaft 19 by means of which it is rewound.

The invention Shaft 19 is driven by motor 20 through a suitable set of reduction gears 21.

Motor 20 includes a U-shaped magnetic frame 22mounted on pivots 23 and 24. A core 25, having wound thereon a coil 26, is

attached to one side of the frame 22, and a pole-piece 27 having a shorted coil 28 thereon is attached to the other side. A disc 29 of conducting material extending into the gap between 25 and 27 and mounted on shaft 30 is caused to rotate when coil 25 is energized by alternating current; A worm 34 mounted on shaft 30 engages the first gear of gear train 21 and constitutes an irreversible drive, so that in' case the motor stops the spring may still drive the clock mechanism for a considerable time. The torque exerted by disc 29 depends upon the position of the coil 28 on pole 27. The alternating flux passing through the disc is converted into a shifting flux by the coil 28 and the amount of shift, tangential to the direction of rotation, determines the torque exerted by disc 29. When the spring becomes wound the force required to turn the disc becomes greater. Helical spring 31 is however adjusted, by means of clamping nut 33, to hold frame 22 in its normal position against stop 32 with a force which when multiplied through the reduction gearing amounts to the maximum desired countertorque of. the main spring. Any tendency to wind the spring to a greater tension causes the poles to shift from the normal position in a direction opposite to the direction of rotation of the disc, and into a position such as indicated by dotted lines in Fig. 3. The coil 28 is then in a position causing less shifting of the flux tangential to the disc 29 and, therefore, less torque exerted by the disc 29. This displacement of course continues until the force of spring 31 is balanced against the counter-torque of the main spring through the gearing.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown and described is only an illustration and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is 1. An induction disc motor including a rotatable disc armature and a movable stator arranged to control the torque exerted by said armature, and resilient means tending to maintain the stator in a maximum torque producing position but yieldable in response to the motor torque to allow the stator to move to a lower torque producing position, whereby the position of said stator is varied to maintain constant the torque exerted by said armature.

2. In apparatus of the character described, an induction disc motor comprising a rotatively mounted armature and a pivotally mounted stator having thereon for movement therewith a shaded pole element the position of which determines the torque exerted by said armature, and means responsive to the motor torque for controlling the position of said stator.

3. An electric motor including a disc arm-v ature arranged to wind a drivlng spring, a pivotally mounted stator, a spring tending to hold said stator in the maximum-torque operating position and arranged to allow said stator to move into a reduced-torque operating position when the counter-torque of the driving spring has reached a predetermined value.

4. In apparatus of the character described an induction motor comprising a rotatably mounted induction disc armature and a stator element having an energizing winding and shaded pole for producing a shifting flux through said disc, said stator e1c ment being pivoted for limited rotation about an axis parallel to the axis of rotation of said disc, a spring adapted to hold said stator element in a position where the direction of flux shift corresponds to the direction of movement of said disc when the motor torque is small and to yield in response to an increase in motor torque to permit said stator to move into a position Where the direction of flux shift is at an angle to the direction of movement of said disc.

In witness whereof, I have hereunto set my hand this 9th day of April, 1928.

' CHESTER I. HALL. 

